A variety of devices have been employed to remove volatile compounds, especially, volatile organic compounds from a gas stream such as air. For example, U.S. Pat. No. 5,354,540 discloses a device in the form of a catalytic air purification device which operates at low temperatures for the removal of volatile organic compounds from an ambient air space. The air passes through a structure coated with a catalyst which catalytically oxidizes the compounds. The structure is preferably in the form of a honeycomb and is heated by an electric heating element.
Japanese Patent Document No. 61-161,121 discloses a deodorizer employing a blower and a deodorizing filter with an effective-life indicator installed on the suction side of the deodorizing filter or on the blowing side. A color change is observed in the effective-life indicator according to the offensive-odor component removed from the gas stream.
The above-mentioned devices either employ a catalyst system for converting volatile compounds to different compounds through a chemical reaction or employ a filtering system and a separate indicator system which add significant complexity to such devices.
U.S. Pat. Nos. 4,938,939 and 5,346,535, each incorporated herein by reference, teach a new class of adsorbent materials principally based on zeolites which have very fine pore sizes. U.S. Pat. No. 4,795,482 discloses a process of absorbing odors through the use of a crystalline siliceous molecular sieve material having pore sizes of at least 5.5 Angstroms.
While devices for catalyzing the destruction of volatile compounds or employing systems having separate filter and indicator systems are known in the art as indicated above, there remains a need to provide an effective means of removing and retaining volatile compounds within a device. There is also a need to provide a visual system for determining the relative capacity of the device to continue to remove and retain such compounds, to identify the particular compounds or classes of compounds that are removed from the gas stream, and/or to provide an indication of the relative amount of such compounds removed from the gas stream.